Image sensing device

ABSTRACT

Image sensing devices are disclosed. In some implementations, an image sensing device may include a first sensor layer structured to include a plurality of first photoelectric conversion elements to receive light rays and generate photocharge corresponding to the light rays, a second sensor layer disposed below the first sensor layer, the second sensor layer structured to include a plurality of second photoelectric conversion element vertically overlapping the first photoelectric conversion elements to receive light rays and generate photocharge corresponding to the light rays having passed through the first sensor layer, and a bonding layer disposed between the first and second sensor layers, wherein the bonding layer comprises a lens layer structured to refract light rays having passed through the first sensor layer toward the second sensor layer such that an angle of incidence of the light rays is larger than a refraction angle of the light rays.

CROSS-REFERENCES TO RELATED APPLICATION

The present application claims the priority and benefits of Koreanapplication number 10-2020-0170452, filed on Dec. 8, 2020, which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

Various embodiments generally relate to an image sensing deviceincluding a photoelectric conversion element implemented in a stackedtype.

BACKGROUND

An image sensing device is a device for capturing optical images byconverting light into electrical signals using a photosensitivesemiconductor material which reacts to light. With the development ofautomotive, medical, computer and communication industries, the demandfor high-performance image sensing devices is increasing in variousfields such as smart phones, digital cameras, game machines, IOT(Internet of Things), robots, security cameras and medical microcameras.

The image sensing device may be roughly divided into CCD (Charge CoupledDevice) image sensing devices and CMOS (Complementary Metal OxideSemiconductor) image sensing devices. The CCD image sensing devicesoffer a better image quality, but they tend to consume more power andare larger as compared to the CMOS image sensing devices. The CMOS imagesensing devices are smaller in size and consume less power than the CCDimage sensing devices. Furthermore, CMOS sensors are fabricated usingthe CMOS fabrication technology, and thus photosensitive elements andother signal processing circuitry can be integrated into a single chip,enabling the production of miniaturized image sensing devices at a lowercost. For these reasons, CMOS image sensing devices are being developedfor many applications including mobile devices.

SUMMARY

The embodiments of the disclosed technology relate to an image sensingdevice having an optimized stack structure.

In some embodiments of the disclosed technology, an image sensing devicehas two or more image sensor layers stacked on top of one another andone or more bonding layers arranged between two or more image sensorlayers. The one or more bonding layers may include one or more lensesstructured to correct or adjust light path from one image sensor layerto another image sensor layer.

In an embodiment, an image sensing device may include: a first sensorlayer structured to include a plurality of first photoelectricconversion elements to receive light rays and generate photochargecorresponding to the light rays; a second sensor layer disposed belowthe first sensor layer, the second sensor layer structured to include aplurality of second photoelectric conversion element verticallyoverlapping the first photoelectric conversion elements to receive lightrays and generate photocharge corresponding to the light rays havingpassed through the first sensor layer; and a bonding layer disposedbetween the first and second sensor layers, wherein the bonding layercomprises a lens layer structured to refract light rays having passedthrough the first sensor layer toward the second sensor layer such thatan angle of incidence of the light rays is larger than a refractionangle of the light rays.

In an embodiment, an image sensing device may include: a plurality offirst photoelectric conversion elements structured to respond toincident light, each first photoelectric conversion element structuredto convert the incident light into a first electrical signal; aplurality of second photoelectric conversion elements disposed under theplurality of first photoelectric conversion elements verticallyoverlapping the plurality of first photoelectric conversion elements,each second photoelectric conversion element structured to convert theincident light that passes through a first sensor layer into a secondelectrical signal; and a lens layer disposed under the plurality offirst photoelectric conversion elements and over the plurality of secondphotoelectric conversion elements, wherein the lens layer comprises afirst slit having a first width, a second slit having a second widthnarrower than the first width, and a dielectric layer structured tosurround the first and second slits, and the first slit is disposed at aposition where a chief ray incident on the lens layer reaches.

In an embodiment, an image sensing device may include: a first sensorlayer including a first photoelectric conversion element configured togenerate photocharge corresponding to the intensity of light; a secondsensor layer including a second photoelectric conversion elementvertically overlapping the first photoelectric conversion element, andconfigured to generate photocharge corresponding to the intensity oflight having passed through the first sensor layer; and a bonding layerdisposed between the first and second sensor layers. The bonding layermay include a digital lens configured to refract light having passedthrough the first sensor layer, such that an incident angle of the lightis larger than a refraction angle of the light.

In an embodiment, an image sensing device may include: a firstphotoelectric conversion element configured to generate photochargecorresponding to the intensity of light; a second photoelectricconversion element vertically overlapping the first photoelectricconversion element, and configured to generate photocharge correspondingto the intensity of light having passed through the first sensor layer;and a digital lens disposed between the first and second photoelectricconversion elements, wherein the digital lens includes a first slithaving a relatively large width, a second slit having a relatively smallwidth, and a dielectric layer disposed between the first and secondslits, and the first slit is disposed at a position which a chief rayincident on the digital lens reaches.

In an embodiment, an image sensing device may include: a substrate; afirst sensor layer supported by the substrate and structured to includea plurality of first photoelectric conversion elements to receive lightrays and generate photocharge corresponding to the light rays; a secondsensor layer supported by the substrate and disposed below the firstsensor layer, the second sensor layer structured to include a pluralityof second photoelectric conversion element vertically overlapping thefirst photoelectric conversion elements to receive light rays andgenerate photocharge corresponding to the light rays having passedthrough the first sensor layer; and a bonding layer disposed in thesubstrate between the first and second sensor layers, wherein thebonding layer comprises a lens layer structured to refract light rayshaving passed through the first sensor layer toward the second sensorlayer such that an angle of incidence of the light rays is larger than arefraction angle of the light rays.

In an embodiment, an image sensing device may include: a substrate; aplurality of first photoelectric conversion elements supported by thesubstrate and structured to respond to incident light, each firstphotoelectric conversion element structured to convert the incidentlight into a first electrical signal; a plurality of secondphotoelectric conversion elements supported by the substrate anddisposed under the plurality of first photoelectric conversion elementsvertically overlapping the plurality of first photoelectric conversionelements, each second photoelectric conversion element structured toconvert the incident light that passes through the first sensor layerinto a second electrical signal; and a lens layer disposed in thesubstrate under the plurality of first photoelectric conversion elementsand over the plurality of second photoelectric conversion elements,wherein the lens layer comprises a first slit having a first width, asecond slit having a second width narrower than the first width, and adielectric layer structured to surround the first and second slits, andthe first slit is disposed at a position where a chief ray incident onthe lens layer reaches.

In some embodiments, the digital lens may be inserted between thephotoelectric conversion elements that are vertically stacked, andcalibrate the optical path, thereby preventing optical crosstalk.

In addition, it is possible to provide various effects which aredirectly or indirectly understood through this document.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating an example configurationof an image sensing device based on an embodiment of the disclosedtechnology.

FIG. 2 is a diagram illustrating an example of a stacked structure of afirst sensor layer, a second sensor layer and a logic layer illustratedin FIG. 1.

FIG. 3 is a cross-sectional view of the stacked structure illustrated inFIG. 2.

FIG. 4 is a diagram illustrating an example of light rays that propagatetoward the first sensor layer through a lens module.

FIG. 5 is a diagram illustrating an example of the stacked structurecorresponding to a center region of FIG. 4.

FIG. 6 is a diagram illustrating an example of the stacked structurecorresponding to a first edge region of FIG. 4.

FIG. 7 is a diagram illustrating another example of the stackedstructure corresponding to the first edge region of FIG. 4.

FIG. 8 is a diagram illustrating another example of the stackedstructure corresponding to the first edge region of FIG. 4.

DETAILED DESCRIPTION

Hereafter, various embodiments of the present disclosure will bedescribed with reference to the accompanying drawings. However, itshould be noted that the present disclosure is not limited to specificembodiments, but includes various modifications, equivalents and/oralternatives.

FIG. 1 is a diagram schematically illustrating an example configurationof an image sensing device based on an embodiment of the disclosedtechnology.

Referring to FIG. 1, an image sensing device 100 is a CMOS(Complementary Metal-Oxide-Semiconductor) image sensing device, and mayinclude a light source 10, a lens module 20, a first sensor layer 200, asecond sensor layer 300 and a logic layer 400.

Depth sensors are used to measure a distance between image sensingdevice and an object. The depth sensors may require an extra space inthe electronic device, bringing restrictions to the design of the imagesensing device.

The first and second sensor layers 200 and 300 may acquire the same typeof images or different types of images, respectively. In someimplementations, the first sensor layer 200 may be used to acquire acolor image corresponding to a specific color (e.g., R (Red), G (Green)or B (Blue)), and the second sensor layer 300 may be used to acquire adepth image for measuring the distance between the image sensing deviceand a target object 1 through a ToF (Time of Flight) method. In someimplementations, the image sensing device 100 acquires a color image anda depth image. In some implementations, the depth image may include animage or optical signal captured by an image sensor to measure adistance between image sensing device and an object.

In an implementation, the image sensing device 100 may acquire a colorimage and an IR (Infrared-Ray) image concurrently. In anotherimplementation, the image sensing device 100 may acquire a pair of colorimages corresponding to different sensitivities. In this case, the imagesensing device 100 may not include some of the components other imagesensing device can have, such as the light source 10 and a light sourcedriver 420 of the logic layer 400.

The light source 10 emits light toward the target object 1 in responseto a modulation light signal MLS from the logic layer 400. Examples ofthe light source 10 may include an laser diode (LD) or a light emittingdiode (LED), an NIR (Near Infrared Laser), a point light source, amonochromatic illumination source and a combination of these lightsources and/or other laser sources. The LD or the LED emits light at aspecific wavelength band (e.g., near-infrared ray, infrared ray orvisible light), and the monochromatic illumination source include awhite lamp and a monochromator. For example, the light source 10 mayemit infrared light having a wavelength of 800 nm to 1,000 nm. The lightgenerated by the light source 10 may include light modulated at a presetfrequency. FIG. 1 illustrates only one light source 10 for convenienceof description, but a plurality of light sources may be arranged aroundthe lens module 20.

The lens module 20 may collect light reflected from the target object 1and transfer the collected light to the sensor layers 200 and 300. Thelight reflected from the target object 1 may include infrared light thatis generated by the light source 10 and reflected by the target object1, and visible light that is generated by an external light source(e.g., sunlight or illumination) and reflected by the target object 1.Light reflected from the target object 1 (e.g., an object or a scene) istransmitted through the lens module 20. For example, the lens module 20may include a focusing lens having a glass or plastic surface or acylindrical optical element. The lens module 20 may include a pluralityof lenses aligned with an optical axis.

The first sensor layer 200 may include a plurality of color pixels forcapturing images with colors arranged in rows and columns in a 2D matrixarray. The plurality of color pixels are adjacent image sensing pixelswith different color filters that are arranged to capture colorinformation. For example, the color filters may be arranged based on aBayer filter pattern with green, red and blue filters with 50% green,25% red and 25% blue. The image sensing pixels may be formed in asemiconductor substrate, and may be used to convert light transmittedthrough the lens module 20 and the color filters into electrical signalscorresponding to the intensity of light at a wavelength corresponding toa specific color filter, and output the electrical signals as imagesensing pixel signals.

The second sensor layer 300 may include a plurality of depth pixelsarranged in rows and columns in a 2D matrix array. The depth pixels maybe formed in the semiconductor substrate, and may be used to convertlight transmitted through the lens module 20 into electrical signalscorresponding to the intensity of light at infrared wavelengths, andoutput the electrical signals as depth pixel signals. In someimplementations, the depth pixel signals may be used to measure adistance between image sensing device and an object.

Each of the image sensing pixels and each of the depth pixels mayinclude a photoelectric conversion element to generate photochargescorresponding to the intensity of incident light and one or moretransistors configured to generate an electrical signal based on thephotocharges. For example, each of the image sensing pixels may have a3-TR (transistor) structure, 4-TR structure or 5-TR structure. In someimplementations, each of the depth pixels may include an SPAD (SinglePhoton Avalanche Diode) pixel to be operated based on a direct ToFmethod. In some implementations, each of the depth pixels may be a CAPD(Current Assisted Photonics Demodulation) pixel that can be operatedbased on an indirect ToF method.

The resolution of the image sensing pixels may be equal to or differentfrom the resolution of the depth pixels. In some implementations, theresolution of the depth pixels may be smaller than the resolution of theimage sensing pixels. In some implementations, the first and secondsensor layers 200 and 300 have the same resolution, and the imagesensing pixels are mapped to the depth pixels, respectively.

The logic layer 400 may include circuitry that can control the lightsource 10 to transmit light toward the target object 1, activate thepixels of the first and second sensor layers 200 and 300, and generate acolor image and depth image for the target object 1 by processing animage sensing pixel signal and depth pixel signal corresponding to lightreflected from the target object 1. The color image may be an imageindicating the color of the target object 1, and the depth image may bean image indicating the distance to the target object 1.

The logic layer 400 may include a sensor driver 410, a light sourcedriver 420, a timing controller (T/C) 430 and a logic circuit 440.

The sensor driver 410 may activate and/or control the image sensingpixels of the first sensor layer 200 and the depth pixels of the secondsensor layer 300 in response to a timing signal generated by the timingcontroller 430. For example, the sensor driver 410 may generate acontrol signal to select and control one or more row lines among aplurality of row lines of each of the first and second sensor layers 200and 300. Such a control signal may include a reset signal forcontrolling a reset transistor, a transmission signal for controlling atransmission transistor, a selection signal for controlling a selectiontransistor, and the like. In some implementations, when the secondsensor layer 300 includes pixels that are operated based on the indirectToF method, the control signal may further include a demodulationcontrol signal having a specific phase difference (e.g., 0, 90, 180 or270 degrees) from the modulation light signal MLS.

The light source driver 420 may generate the modulation light signal MLSto control the light source 10 based on commands or control signalsgenerated by the timing controller 430. The modulation light signal MLSmay include a signal modulated at a preset frequency.

The timing controller 430 may generate a timing signal for controllingthe operations of the sensor driver 410, the light source driver 420 andthe logic circuit 440.

The logic circuit 440 may generate digital pixel data by processinganalog pixel signals generated by the first and second sensor layers 200and 300 based on commands or control signals generated by the timingcontroller 430. In some implementations, the logic circuit 440 mayinclude a CDS (Correlated Double Sampler) configured to performcorrelated double sampling on the pixel signals outputted from the firstand second sensor layers 200 and 300. The logic circuit 440 may includean ADC (Analog-Digital Converter) configured to convert analog outputsignals from the CDS into digital signals. In some implementations, thelogic circuit 440 may include a buffer circuit configured to temporarilystore pixel data outputted from the ADC and output the pixel data basedon commands or control signals generated by the timing controller 430.

In some implementations, the logic circuit 440 may generate a colorimage based on the light rays captured by the first sensor layer 200 anda depth image based on the light rays captured by the second sensorlayer 300. In some implementations, an image signal processor (notillustrated) provided in addition to the logic circuit 440 or the imagesensing device 100 may generate a 3D image by synthesizing the colorimage and the depth image, or determine the distance between the secondsensor layer 300 and the target object 1 based on the depth image.

By way of example of the method for calculating the distance to thetarget object 1, the indirect ToF method will be discussed below. Thelight source 10 may generate light rays that are modulated at the presetfrequency, toward a target object. The image sensing device 100 maygenerate a depth image of the depth pixels by sensing the modulatedlight rays reflected from the target objects 1. In some implementations,a time delay that occurs between the modulated light and the incidentlight is used to determine the distance between the image sensing device100 and the target object 1. Such a time delay results in a phasedifference between a signal generated by the image sensing device 100and the modulation light signal MLS for controlling the light source 10.The image signal processor (not illustrated) may calculate depthinformation for each depth pixel by calculating the phase differencewith respect to the depth image outputted from the image sensing device100.

FIG. 2 is a diagram illustrating an example of a stacked structure ofthe first sensor layer, the second sensor layer and the logic layerillustrated in FIG. 1.

Referring to FIG. 2, the first sensor layer 200, the second sensor layer300 and the logic layer 400 of the image sensing device 100 illustratedin FIG. 1 may be stacked on top of one another and aligned with theoptical axis OA of the lens module 20.

In some implementations, a bonding layer 500 may be disposed between thefirst sensor layer 200 and the second sensor layer 300 to bond the firstand second sensor layers 200 and 300 and to transfer signals to thelogic layer 400. In some implementations, the first sensor layer 200,the bonding layer 500, the second sensor layer 300 and the logic layer400 may be sequentially arranged in the direction away from the lensmodule 20. Although FIG. 2 illustrates the first sensor layer 200, thebonding layer 500, the second sensor layer 300 and the logic layer 400as having the same cross sectional area, the disclosed technology is notlimited thereto.

The cross-sectional region of the first sensor layer 200, the bondinglayer 500, the second sensor layer 300 and the logic layer 400, whichare stacked on top of one another, may be divided into a center regionCR and an edge region ER, as shown in FIG. 2.

The center region CR, through which the optical axis OA passes, mayinclude pixels corresponding to a predetermined number of rows andcolumns. FIG. 2 illustrates that the center region CR is formed in arectangular shape, but the disclosed technology is not limited thereto.For example, the center region CR may have a cross-sectional shapecorresponding to the shape of the lens module 20.

The edge region ER, which surrounds the center region CR, may includepixels.

FIG. 3 is a cross-sectional view of the stacked structure illustrated inFIG. 2.

FIG. 3 illustrates the cross-section of the stacked structure of thefirst sensor layer 200, the bonding layer 500, the second sensor layer300 and the logic layer 400, which are illustrated in FIG. 2, withrespect to three pixels only by way of example.

The first sensor layer 200, the bonding layer 500, the second sensorlayer 300 and the logic layer 400 are stacked in the sequence asillustrated in FIG. 3.

The first sensor layer 200 may include a first substrate 210, a firstphotoelectric conversion element 220, an optical filter 230 and amicrolens 240.

The first substrate 210 may include top and bottom surfaces facing awayfrom each other. In one example, the first substrate 210 may be a P-typeor N-type bulk substrate. In another example, the first substrate 210may be a substrate formed through an epitaxial growth of a P-type orN-type epitaxial layer on a P-type bulk substrate. In another example,the first substrate 210 may be a substrate formed through an epitaxialgrowth of a P-type or N-type epitaxial layer on an N-type bulksubstrate.

The first photoelectric conversion element 220 may be disposed at aregion within the first substrate 210, corresponding to each imagesensing pixel. The first photoelectric conversion element 220 maygenerate photocharges corresponding to the intensity of light at aspecific visible light wavelength band. The first photoelectricconversion element 220 may have a large light receiving area to improveefficiency by having a large fill-factor. Examples of the firstphotoelectric conversion element 220 may include a photodiode, aphototransistor, a photogate, a pinned photoelectric conversion elementor combinations thereof.

When the first photoelectric conversion element 220 is implemented as aphotodiode, the first photoelectric conversion element 220 may be formedas an N-type doping region by implanting N-type ions through an ionimplantation process. In an embodiment, the photo diode may have astructure in which two or more doping regions are stacked. In this case,a lower doping region may be formed by implanting P ions and N+ ions,and an upper doping region may be formed by implanting N− ions.

The optical filter 230 may be formed over the first substrate 210, andselectively transmit light at a specific wavelength band correspondingto the visible light wavelength band (e.g., red, green or blue light).In some implementations, the optical filter 230 may include a colorfilter without an infrared cut-off filter. Thus, light having passedthrough the optical filter 230 may include light rays at a specificvisible light wavelength band and an infrared light wavelength band,corresponding to the optical filter 230. The infrared light has a largerwavelength than the visible light, and thus can penetrate through athicker material layer than the visible light. Therefore, even when thevisible light having passed through the optical filter 230 is absorbedby the first photoelectric conversion element 220, the infrared lighthaving passed through the optical filter 230 may reach the bonding layer500 after passing through the first photoelectric conversion element220.

The microlens 240 may be formed in a hemispherical shape over theoptical filter 230 to improve the light receiving efficiency byincreasing the light gathering power of the microlens 240. In someimplementations, the microlens 240 may additionally include anover-coating layer (not illustrated) formed at the top or bottom thereofto avoid lens flare by preventing diffused reflection of light.

Although not illustrated in FIG. 3, a source and drain may be formed inan internal region of the first substrate 210 that is adjacent to thebottom surface of the first substrate 210. The source and drain mayconstitute each of a plurality of transistors for generating pixelsignals based on photocharges that are accumulated in the firstphotoelectric conversion element 220. The plurality of transistors maybe provided for each pixel or each pixel group of four pixels, forexample. In an embodiment, each of the source and drain may include animpurity region doped with P-type or N-type impurities.

Pixel gates (not illustrated) constituting the transistor with thesource and drain included in the first substrate 210 may be formed in aninternal region of the bonding layer 500 adjacent to the bottom surfaceof the first substrate 210. The pixel gates may generate image sensingpixel signals by operating based on a control signal, such that eachimage sensing pixel can generate an image sensing pixel signalcorresponding to the photocharges generated by the first photoelectricconversion element 220. For example, the pixel gates may include resetgates constituting a reset transistor, transmission gates constituting atransmission transistor, and selection gates constituting a selectiontransistor. Each of the pixel gates may include a gate dielectric layerfor electrical isolation from the first substrate 210 and a gateelectrode configured to receive the control signal.

The second sensor layer 300 may include a second substrate 310 and asecond photoelectric conversion element 320.

In some implementations, the second substrate 310 and the secondphotoelectric conversion element 320 have the same functions as those ofthe first substrate 210 and the first photoelectric conversion element220 of the first sensor layer 200 and are fabricated in the same manneras the first substrate 210 and the first photoelectric conversionelement 220.

In some implementations, the second photoelectric conversion element 320may generate photocharges corresponding to the intensity of incidentlight that reaches the second photoelectric conversion element 320 afterpassing through the bonding layer 500 without being absorbed (orphotoelectrically converted) by the first photoelectric conversionelement 220. In some implementations, the first photoelectric conversionelement 220 and the second photoelectric conversion element 320 mayvertically overlap each other.

In an embodiment, an isolation layer may be formed between the firstphotoelectric conversion elements 220 adjacent to each other and/or thesecond photoelectric conversion elements 320 adjacent to each other. Theisolation layer may have a DTI (Deep Trench Isolation) structure. Insome implementations, the isolation layer may be formed by etching thesubstrate on the left and right sides of the photoelectric conversionelement 220 or 320 in a vertical direction through a deep-trench processto form trenches and gap-filling the trenches with a dielectric materialhaving a different refractive index (e.g., a relatively high refractiveindex) from the corresponding substrate 210 or 310.

Although not illustrated in FIG. 3, a source and drain may be formed inan internal region of the second substrate 310 that is adjacent to thetop surface of the second substrate 310. The source and drain mayconstitute each of a plurality of transistors for generating pixelsignals based on photocharges that are accumulated in the secondphotoelectric conversion element 320. The plurality of transistors maybe provided for each pixel or each pixel group of four pixels, forexample. In an embodiment, each of the source and drain may include animpurity region doped with P-type or N-type impurities.

Pixel gates (not illustrated) constituting the transistor with thesource and drain included in the second substrate 310 may be formed inan internal region of the bonding layer 500, adjacent to the top surfaceof the second substrate 310. The pixel gates may generate a depth pixelsignal by operating based on the control signal, such that each depthpixel can generate a depth pixel signal corresponding to thephotocharges generated by the second photoelectric conversion element320. For example, the pixel gates may include reset gates constituting areset transistor, transmission gates constituting a transmissiontransistor, and selection gates constituting a selection transistor.Each of the pixel gates may include a gate dielectric layer forelectrical isolation from the second substrate 310 and a gate electrodeconfigured to receive the control signal.

The bonding layer 500 may be disposed between the first and secondsensor layers 200 and 300 to bond the first and second sensor layers 200and 300 to each other. The bonding layer 500 may include a interconnectregion 510, a first TSV (Through Silicon Via) pad 520 and a second TSVpad 530.

The interconnect region 510 may include a plurality of interconnectlayers (e.g., Ma to Md of FIG. 5), and pixel gates and metalinterconnects may be disposed in the plurality of interconnect layers.

The pixel gates may be configured in the same manner as those describedabove with respect to the first and second sensor layers 200 and 300.

Metal interconnects (540 of FIG. 5, for example) may transfer a controlsignal from the first or second TSV pad 520 or 530 to the pixel gates,and transfer an image sensing pixel signal or depth pixel signal,generated by operations of the pixel gates, to the first or second TSVpad 520 or 530.

In some implementations, no or less metal interconnects may be disposedin a region corresponding to the bottom of the first photoelectricconversion element 220 (or the top of the second photoelectricconversion element 320) such that light having passed through the firstsensor layer 200 can be effectively transmitted to the second sensorlayer 300.

The first TSV pad 520 may be disposed at the uppermost layer (e.g., Mdof FIG. 5) among the plurality of interconnect layers, and electricallycoupled to the metal interconnects and a first TSV 525 and transfer anelectrical signal (e.g., a control signal or image sensing pixelsignal). The first TSV pad 520 may have a larger horizontal area thanthe first TSV 525. The first TSV pad 520 may be disposed in the edgeregion where no image sensing pixels are disposed.

The second TSV pad 530 may be disposed at the lowermost layer (e.g., Maof FIG. 5) among the plurality of interconnect layers, and may beelectrically coupled to the metal interconnects and a second TSV 535 tocarry an electrical signal (e.g., a control signal or a depth pixelsignal). The second TSV pad 530 may have a larger horizontal area thanthe second TSV 535. The second TSV pad 530 may be disposed in the edgeregion where no pixels are disposed.

As described with reference to FIG. 1, the logic layer 400 may perform aseries of operations for generating a color image and a depth image. Thelogic layer 400 may include a third TSV pad 410.

The third TSV pad 410 may be electrically coupled to the first andsecond TSVs 525 and 535 and logic circuits inside the logic layer 400,and may be used to transmit electrical signals (e.g., a control signal,an image sensing pixel signal and a depth pixel signal). The third TSVpad 410 may have a larger horizontal area than the first and second TSVs525 and 535. The third TSV pad 410 may be disposed so that at least apart thereof vertically overlaps the first TSV pad 520 corresponding tothe first sensor layer 200 and the second TSV pad 530 corresponding tothe second sensor layer 300.

The TSV pads 520, 530 and 410 and the metal interconnects of theinterconnect region 510 may include silver (Ag), copper (Cu), aluminum(Al) or other materials that have electrical conductivity. The TSV pads520 and 410 may be electrically coupled through the first TSV 525, andthe TSV pads 530 and 410 may be electrically coupled through the secondTSV 535.

The first and second TSVs 525 and 535 may be electrically connected tothe corresponding TSV pads vertically through at least parts of thebonding layer 500, the second sensor layer 300 and the logic layer 400.

In some implementations, each of the first and second TSVs 525 and 535may have a dual structure including an internal plug for electricalcoupling and a barrier surrounding the internal plug to electricallyisolate the internal plug. The internal plug may include Ag, Cu, Al orthe like, which has high electrical conductivity. The barrier mayinclude titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalumnitride (TaN) or at least one of other barrier metals.

FIG. 4 is a diagram illustrating an example of light rays that propagatetoward the first sensor layer through the lens module.

FIG. 4 illustrates a cross-section of the image sensing device 100 ofFIG. 2. The image sensing device 100 may be divided into a center regionCR including the optical axis OA, a first edge region ER1 disposed onone side (i.e., left side) of the center region CR, and a second edgeregion ER2 disposed on the other side (i.e., right side) of the centerregion CR. The first and second edge regions ER1 and ER2 may be includedin the edge region ER of FIG. 2.

A chief ray CR1 incident on the center region CR through the lens module20 may be vertically incident on the top surface of the first sensorlayer 200. That is, the angle of incidence of the chief ray incident onthe center region CR may be 0 degree or an angle approximate to 0degree.

However, the chief ray incident on the first and second edge regions ER1and ER2 may be incident obliquely on the top surface of the first sensorlayer 200. That is, the angle of incidence of a chief ray CR2 incidenton the first edge region ER1 and the angle of incidence of a chief rayCR3 incident on the second edge region ER2 may correspond to apredetermined angle ranging from 0 to 90 degrees. The predeterminedangle may be changed depending on the size of the first sensor layer200, the curvature of the lens module 20, the distance between the lensmodule 20 and the first sensor layer 200 or the like.

The angles of incidence of the chief rays CR1 to CR3 may graduallyincrease from the optical axis OA toward both ends of the first sensorlayer 200.

FIG. 5 is a diagram illustrating an example of the stacked structurecorresponding to the center region of FIG. 4.

In some implementations, the stacked structure STK-CR may include thefirst sensor layer 200, the second sensor layer 300 and the bondinglayer 500 in the center region CR. By way of example, FIG. 5 illustratescross-sections of three adjacent pixels of the first sensor layer 200and three adjacent pixels of the second sensor layer 300. In someimplementations, the other pixels within the center region CR may havethe same structure as the pixels illustrated. FIG. 5 illustrates firstto third pixel groups PX1 to PX3, and each of the pixel groups PX1 toPX3 may include the pixels of the first and second sensor layers 200 and300. The pixels include photoelectric conversion elements verticallyoverlap each other. Suppose that the center axis of the first pixelgroup PX1, a straight line that is parallel to the optical axis OApassing through the center of the photoelectric conversion element 220within the pixel of the first sensor layer 200 included in the firstpixel group PX1, a straight line that is parallel to the optical axis OApassing through the center of the photoelectric conversion element 320within the pixel of the second sensor layer 300 included in the firstpixel group PX1, and a straight line that is parallel to the opticalaxis OA passing through the center of a digital lens 600 coincide withone another. Such a supposition may be similarly applied to the otherpixel groups which will be described below. Furthermore, the center axisof a pixel group is defined as a pixel center line.

In some implementations, the internal structures of the first and secondsensor layers 200 and 300 are the same as those discussed above withreference to FIG. 3.

The bonding layer 500 may include the plurality of interconnect layersMa to Md. The plurality of interconnect layers Ma to Md may be includedin the interconnect region 510 described with reference to FIG. 3.

The first interconnect layer Ma, the second interconnect layer Mb, thethird interconnect layer Mc and the fourth interconnect layer Md may besequentially stacked from bottom to top in FIG. 5. During a fabricationprocess of the bonding layer 500, the plurality of interconnect layersMa to Md may be stacked in the order of the fourth to first interconnectlayers Md to Ma or the first to fourth interconnect layers Ma to Md inFIG. 5.

The bonding layer 500 may include pixel gates, metal interconnects 540,a dielectric layer 550 and the digital lens 600.

The pixel gates may be disposed in the interconnect layer Md adjacent tothe bottom surface of the first substrate 210 or the interconnect layerMa adjacent to the top surface of the second substrate 310. The metalinterconnects 540 may be disposed in the interconnect layers Ma to Md,respectively, and metal interconnects included in different interconnectlayers may be electrically coupled to each other through the dielectriclayer 550. Since the pixel gates and the metal interconnects 540 havebeen described with reference to FIG. 3, the overlapping descriptionsthereof will be omitted herein.

The dielectric layer 550 may surround the metal interconnects 540,electrically insulating the metal interconnects 540. In someimplementations, the dielectric layer 550 may include at least one ofsilicon oxide, silicon nitride and silicon oxynitride.

Where the first sensor layer 200 structured to generate the color imageis arranged over the second sensor layer 300 structured to generate thedepth image, the disclosed technology can be implemented in someembodiments to provide a lens layer arranged below the first sensorlayer 200 and above the second sensor layer 300 to modify the paths oflight transmitted to the second sensor layer 300. The digital lens 600may calibrate an optical path of the light transmitted through the firstsensor layer 200 to increase the amount of light rays that reach thesecond sensor layer 300. The operation of calibrating the optical pathmay indicate an operation of refracting light such that an angle ofincidence with respect to the digital lens 600 is larger than arefraction angle.

The digital lens 600 may include one or more first slits 610 having arelatively large width and one or more second slits 620 having arelatively small width. Furthermore, the digital lens 600 may includethe dielectric layer 550 disposed to surround the first and second slits610 and 620 and at portions of the digital lens 600 where the first orsecond slit 610 or 620 is not disposed. The number of first slits 610and the number of second slits 620 in FIG. 5 are only examples forillustration purposes, and the disclosed technology is not limitedthereto.

In an implementation, the digital lens 600 may be disposed in the secondinterconnect layer Mb. In another implementation, the digital lens 600may be disposed in another interconnect layer such as the thirdinterconnect layer Mc.

The first and second slits 610 and 620 may each include a materialhaving a higher refractive index than the dielectric layer 550. Thefirst and second slits 610/620 and the dielectric layer 550 in thedigital lens 600 may be arranged such that the cross sections of theslits and the cross sections of the dielectric layer 550 are alternatelyarranged. Although not illustrated, a horizontal cross section of thedigital lens 600 may have loop-shaped dielectric layers 550 and thesecond slits 620 that are alternately disposed around the first slit610.

In some implementations, the digital lens 600 may be formed as will bediscussed below. A photomask is disposed to define regions where thefirst and second slits 610 and 620 will be formed, after the dielectriclayer 550 of the second interconnect layer Mb is formed. An etchingprocess may be performed to form vacant patterns corresponding to thefirst and second slits 610 and 620. The vacant pattern may be gap-filledwith a material having a relatively high refractive index, therebyforming the digital lens 600.

The region where the first slit 610 having a relatively large width isdisposed in the digital lens 600 may become an optically dense region,and the region where the second slit 620 having a relatively small widthis disposed in the digital lens 600 may become an optically less denseregion. The dielectric layer 550 disposed in the interconnect layers Mcand Md over the digital lens 600 may become an optically less denseregion, compared to the region where the second slit 620 is disposed inthe digital lens 600. That is, the refractive indices of media mayincrease in the order of (1) the dielectric layer 550 disposed in theinterconnect layers Mc and Md, (2) the region where the second slit 620is disposed in the digital lens 600, and (3) the region where the firstslit 610 is disposed in the digital lens 600.

Therefore, when light is incident on the digital lens 600 from thedielectric layer 550 disposed in the interconnect layers Mc and Md, thelight propagates from the optically less dense region to the opticallydense region. Thus, the refraction angle of the light is smaller thanthe angle of incidence thereof. Furthermore, since the region where thefirst slit 610 is disposed in the digital lens 600 corresponds to adenser medium than the region where the second slit 620 is disposed inthe digital lens 600, the region where the first slit 610 is disposedhas a smaller refraction angle than the region where the second slit 620is disposed.

A chief ray L1 incident on each of the first to third pixel groups PX1to PX3 included in the center region CR may enter the top surface of thefirst substrate 210 in the direction perpendicular to the top surface ofthe first substrate 210 and pass through the pixel center line of eachof the pixel groups PX1 to PX3. Furthermore, the chief ray L1 may passthrough the first slit 610 of the digital lens 600. That is, the firstslit 610 may be disposed at a position of the digital lens 600 that thechief ray L1 reaches.

Since the angle of incidence of the chief ray L1 is 0 degree (or a valueapproximate to 0 degree), a chief ray L1′ having passed through thedigital lens 600 may reach the second photoelectric conversion element320 while having a refraction angle of 0 degree (or a value approximateto 0 degree).

FIG. 6 is a diagram illustrating an example of the stacked structurecorresponding to a first edge region of FIG. 4.

In some implementations, the stacked structure STK-ERa may include thefirst sensor layer 200, the second sensor layer 300 and the bondinglayer 500 in the first edge region ER1. By way of example, FIG. 6illustrates cross-sections of the first to third pixel groups PX1 to PX3including three adjacent pixels of the first sensor layer 200 and threeadjacent pixels of the second sensor layer. In some implementations, theother pixels within the first edge region ER1 may have the samestructure as the pixels illustrated. In some implementations, thestructure of the second edge region ER2 and the structure of the firstedge region ER1 are symmetrical with respect to the optical axis OA, andthus the structure of the second edge region ER2 may have the samestructure as the first edge region ER1.

In the first edge region ER1, the optical filter 230 and the microlens240 may be shifted to the right from the first photoelectric conversionelement 220. That is, the optical filter 230 and the microlens 240 maybe shifted toward the optical axis OA from the pixel center line. Theoptical filter 230 and the microlens 240 may be shifted to differentextents. As illustrated in FIG. 6, the microlens 240 may be shifted morethan the optical filter 230 to effectively perform light collection andfiltering on a chief ray L2 incident on the first to third pixel groupsPX1 to PX3 in the first edge region ER1, because the chief ray L2 isincident obliquely with respect to the top surface of the firstsubstrate 210.

In some implementations, the inner structure of the bonding layer 500 isidentical or similar to what is discussed above with reference to FIG.5, the following descriptions will focus on what is different from thebonding layer 500 of FIG. 5.

The chief ray L2 incident on each of the first to third pixel groups PX1to PX3 included in the first edge region ER1 may be incident obliquelywith respect to the top surface of the first substrate 210, and incidenttoward the left side based on the pixel center line of each of the pixelgroups PX1 to PX3. A first slit 710 of a digital lens 700 may be shiftedto the left from the pixel center line of each of the pixel groups PX1to PX3, and disposed at a position of the digital lens 700 that thechief ray L2 reaches. That is, the first slit 710 may be shifted in theopposite direction to the optical axis OA from the center of the digitallens 700.

In an embodiment, the position of the first slit 710 within the digitallens 700 at the first edge region ER1 may vary, and the first slit 710may be shifted further as the distance to the optical axis OA increases.

The first slit 710 of the digital lens 700 may refract the chief ray L2at a smaller refraction angle than the angle of incidence of the chiefray L2.

When the chief ray L2 has a first angle of incidence, a chief ray L2′having passed through the digital lens 700 may reach the secondphotoelectric conversion element 320 while having a smaller refractionangle than the first angle of incidence.

Furthermore, light rays other than the chief ray L2 incident on a secondslit 720 of the digital lens 700 may also be transferred to the secondphotoelectric conversion element 320 while having a smaller refractionangle than the corresponding angle of incidence.

When it is assumed that the digital lens 700 is not present in thesecond pixel group PX2, the chief ray L2 incident on the second pixelgroup PX2 is not refracted toward the photoelectric conversion element320 of the second pixel group PX2, but is incident on the photoelectricconversion element 320 of the first pixel group PX1 like a chief rayL2″, thereby causing optical crosstalk to degrade a signal-to-noiseratio.

FIG. 7 is a diagram illustrating another example of the stackedstructure corresponding to the first edge region of FIG. 4.

In some implementations, the stacked structure STK-ERb may include thefirst sensor layer 200, the second sensor layer 300 and the bondinglayer 500 in the first edge region ER1. By way of example, FIG. 7illustrates cross-sections of the first to third pixel groups PX1 to PX3including three adjacent pixels of the first sensor layer 200 and threeadjacent pixels of the second sensor layer 300. In some implementations,the other pixels within the first edge region ER1 may have the samestructure as the pixels illustrated. In some implementations, thestructure of the second edge region ER2 and the structure of the firstedge region ER1 are symmetrical with respect to the optical axis OA, andthus the structure of the second edge region ER2 may have the samestructure as the first edge region ER1.

In some implementations, the stacked structure illustrated in FIG. 7 isidentical or similar to what is discussed above with reference to FIG.6, the following descriptions will focus on what is different from FIG.6.

A digital lens 800 may have substantially the same internal structure asthe digital lens 700 of FIG. 6. However, the digital lens 800 may bedisposed in the third interconnect layer Mc located over the secondinterconnect layer Mb.

A chief ray L3 incident on each of the first to third pixel groups PX1to PX3 included in the first edge region ER1 may have a relatively largesecond angle of incidence. In this case, as the chief ray L3significantly deviates from the pixel center line before reaching thesecond interconnect layer Mb, the refraction of light rays by thedigital lens 800 may not be effectively performed.

However, the digital lens 800 disposed in the third interconnect layerMc located over the second interconnect layer Mb may effectively performa refracting operation on the chief ray L3 before the chief ray L3significantly deviates from the pixel center line, thereby transferringa chief ray L3′ having passed through the digital lens 800 to the secondphotoelectric conversion element 320.

When it is assumed that the digital lens 800 is not present in thesecond pixel group PX2, the chief ray L3 incident on the second pixelgroup PX2 is not refracted toward the photoelectric conversion element320 of the second pixel group PX2, but is incident on the photoelectricconversion element 320 of the first pixel group PX1 like a chief rayL3″, thereby causing optical crosstalk to degrade a signal-to-noiseratio.

FIG. 8 is a diagram illustrating another example of the stackedstructure corresponding to the first edge region of FIG. 4.

In some implementations, the stacked structure STK-ERc may include thefirst sensor layer 200, the second sensor layer 300 and the bondinglayer 500 in the first edge region ER1. By way of example, FIG. 8illustrates cross-sections of the first to third pixel groups PX1 to PX3including three adjacent pixels of the first sensor layer 200 and threeadjacent pixels of the second sensor layer 300. In some implementations,the other pixels within the first edge region ER1 may have the samestructure as the pixels illustrated. In some implementations, thestructure of the second edge region ER2 and the structure of the firstedge region ER1 are symmetrical with respect to the optical axis OA, andthus the structure of the second edge region ER2 may have the samestructure as the first edge region ER1.

In some implementations, the stacked structure illustrated in FIG. 8 isidentical or similar to what is discussed above with reference to FIG.6, the following descriptions will focus on what is different from FIG.6.

Digital lenses 900 and 1000 may have substantially the same internalstructure as the digital lens 700 of FIG. 6. However, the digital lens900 may be disposed in the second interconnect layer Mb, and the digitallens 1000 may be disposed in the third interconnect layer Mc. That is,the plurality of digital lenses 900 and 1000 may be stacked in each ofthe pixel groups PX1 to PX3. FIG. 8 illustrates two digital lenses thatare stacked as an example. However, three or more digital lenses may bestacked.

A chief ray L4 incident on each of the first to third pixel groups PX1to PX3 included in the first edge region ER1 may have a relatively largethird angle of incidence. In this case, the chief ray L4 may not berefracted to have a sufficiently small refraction angle even though thechief ray L4 passes through one digital lens. Thus, the chief ray L4 maynot be transferred to the second photoelectric conversion element 320.

However, the plurality of digital lenses 900 and 1000 disposed in thesecond and third interconnect layers Mb and Mc, respectively, may berefracted twice to sufficiently reduce the refraction angle of a chiefray L4′ having passed through the digital lenses 900 and 1000. Thus, thechief ray L4′ may be stably transferred to the second photoelectricconversion element 320.

In an embodiment, in order to maximize the refraction effect by theplurality of digital lenses 900 and 1000, the distance between a firstslit 1010 of the digital lens 1000 and the pixel center line may besmaller than the distance between a first slit 910 of the digital lens900 and the pixel center line to allow the chief ray L4′ to morereliably pass through the first slits 910 and 1010 of the digital lenses900 and 1000.

When it is assumed that the digital lens 900 and 1000 are not present inthe second pixel group PX2, the chief ray L4 incident on the secondpixel group PX2 is not refracted toward the photoelectric conversionelement 320 of the second pixel group PX2, but is incident on thephotoelectric conversion element 320 of the first pixel group PX1 like achief ray L4″, thereby causing optical crosstalk to degrade asignal-to-noise ratio.

The embodiments of the digital lens, described with reference to FIGS. 6to 8, may be combined, if necessary.

For example, the digital lens 700 of FIG. 6 may be disposed in thesecond interconnect layer Mb at a region within the first edge regionE1, which is relatively close to the center region CR. The digital lens800 may be disposed in the third interconnect layer Mc at a region whichis relatively far from the center region CR, as illustrated in FIG. 7,and a digital lens may be disposed in the fourth interconnect layer Mdat a region which is the farthest from the center region CR.Alternatively, as illustrated in FIG. 8, the digital lenses 900 and 1000may be disposed in the second and third interconnect layers Mb and Mc,respectively.

While various embodiments have been described above as specific examplesfor implementing those embodiments, variations and modifications ofthose embodiments and other embodiments can be made based on what isdisclosed and illustrated in this patent document.

What is claimed is:
 1. An image sensing device comprising: a first sensor layer structured to include a plurality of first photoelectric conversion elements to receive light rays and generate photocharge corresponding to the light rays; a second sensor layer disposed below the first sensor layer, the second sensor layer structured to include a plurality of second photoelectric conversion element vertically overlapping the first photoelectric conversion elements to receive light rays and generate photocharge corresponding to the light rays having passed through the first sensor layer; and a bonding layer disposed between the first and second sensor layers, wherein the bonding layer comprises a lens layer structured to refract light rays having passed through the first sensor layer toward the second sensor layer such that an angle of incidence of the light rays is larger than a refraction angle of the light rays.
 2. The image sensing device of claim 1, wherein the lens layer includes a digital lens that comprises: a first slit having a first width; a second slit having a second width that is narrower than the first width; and a dielectric layer structured to surround the first and second slits.
 3. The image sensing device of claim 2, wherein each of the first and second slits has a higher refractive index than the dielectric layer.
 4. The image sensing device of claim 2, wherein the first slit is disposed at a position where a chief ray incident on the digital lens reaches.
 5. The image sensing device of claim 2, wherein the first sensor layer, the second sensor layer and the bonding layer are divided into a center region, through which an optical axis of a lens module for transferring light to the first photoelectric conversion elements passes, and an edge region surrounding the center region, and the digital lens at the center region is disposed in a first interconnect layer of the bonding layer.
 6. The image sensing device of claim 5, wherein the first slit in the edge region is shifted in the opposite direction to the optical axis from the center of the digital lens.
 7. The image sensing device of claim 5, wherein the digital lens in the edge region is disposed in a second interconnect layer of the bonding layer, and wherein the second interconnect layer is disposed over the first interconnect layer.
 8. The image sensing device of claim 5, wherein the digital lens in the edge region is disposed in each of the first interconnect layer of the bonding layer and a second interconnect layer disposed over the first interconnect layer.
 9. The image sensing device of claim 5, wherein a microlens disposed over the first photoelectric conversion element in the edge region is shifted toward the optical axis from the center of the digital lens.
 10. The image sensing device of claim 1, further comprising a logic layer that includes circuitry configured to process electrical signals corresponding to photocharges converted from the light rays by the first and second photoelectric conversion elements.
 11. The image sensing device of claim 10, wherein the logic layer is disposed under the second sensor layer, and the bonding layer and the logic layer are electrically coupled through a Through Silicon Via (TSV) formed through the second sensor layer.
 12. An image sensing device comprising: a plurality of first photoelectric conversion elements structured to respond to incident light, each first photoelectric conversion element structured to convert the incident light into a first electrical signal; a plurality of second photoelectric conversion elements disposed under the plurality of first photoelectric conversion elements vertically overlapping the plurality of first photoelectric conversion elements, each second photoelectric conversion element structured to convert the incident light that passes through a first sensor layer into a second electrical signal; and a lens layer disposed under the plurality of first photoelectric conversion elements and over the plurality of second photoelectric conversion elements, wherein the lens layer comprises a first slit having a first width, a second slit having a second width narrower than the first width, and a dielectric layer structured to surround the first and second slits, and the first slit is disposed at a position where a chief ray incident on the lens layer reaches.
 13. The image sensing device of claim 12, wherein each of the first and second slits has a higher refractive index than the dielectric layer.
 14. The image sensing device of claim 12, wherein the plurality of first photoelectric conversion elements are formed in the first sensor layer, the plurality of second photoelectric conversion elements are formed in a second sensor layer, and the lens layer is formed in a bonding layer structured to bond the first sensor layer to the second sensor layer, and wherein the first sensor layer, the second sensor layer, and the bonding layer are divided into a center region, through which an optical axis of a lens module for transferring light to the first photoelectric conversion elements passes, and an edge region surrounding the center region, and the lens layer at the center region is disposed in a first interconnect layer of the bonding layer.
 15. The image sensing device of claim 14, wherein the first slit in the edge region is shifted in the opposite direction to the optical axis from the center of the lens layer.
 16. The image sensing device of claim 14, wherein the lens layer in the edge region is disposed in a second interconnect layer of the bonding layer, and wherein the second interconnect layer is disposed over the first interconnect layer.
 17. The image sensing device of claim 14, wherein the lens layer in the edge region is disposed in each of the first interconnect layer of the bonding layer and a second interconnect layer disposed over the first interconnect layer. 